Practical nitric oxide measurement employing a nitric oxide-selective electrode

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Abstract
An NO‐selective electrode was developed as an easily applicable tool for a real‐time nitric oxide (NO) measurement. The working electrode (0.2 mm diam) was made from Pt/Ir alloy coated with a three‐layered membrane. The counterelectrode was made from a carbon fiber. When a stable NO donor, S‐nitroso‐N‐acetyl‐dl‐penicillamine, was applied, the electrode current increased in a dose‐dependent fashion. The current and calculated NO concentration showed a linear relationship in the range from 0.2 nM (S/N=1) to 1 μM of NO. The response of the electrode was 1.14±0.09 s. The effects of temperature, pH, and chemicals other than NO on the electrode current were also evaluated. Electrodes which were placed in the luminal side of rat aortic rings exhibited 30 pA of current due to NO generation induced by the addition of 10−6 M of acetylcholine. The current was eliminated in the presence of 50 μM NG‐monomethyl‐L‐arginine, an inhibitor of NO synthase. Thus, this NO‐selective electrode is applicable to real‐time NO assay in biological systems.